The present invention relates to waste compacting in particular for disposable packaging, made of cardboard or similar materials, based on organic resins for instance, (and plastics in general), in a machine able of shredding and compressing such waste and thus substantially reducing the volume thereof. Such compacted waste is generally gathered in a movable and exchangeable receptacle of the machine, for instance a transport bag.
Within this frame, the object of the invention essentially resides in a compacting method, which allows eliminating any clogging risk that would cause a machine failure during a compacting operation, as well as in a machine including proper means for implementing the various steps of such method.
A machine presently applied for compacting cardboard and other disposable packaging is described in French Patent Application 97 12 967, filed Oct. 16, 1997. It essentially includes a cylindrical, open-top waste reception tank, and a compacting head comprising a toothed roller that is arranged in said tank and bears on said waste under its own weight. The toothed roller is subject to two rotation motions: a first rotation wherein the top of the compacting head is pivoted around the central tank axis, which is vertically oriented in normal operation, and a second rotation wherein the roller is rotated around its own longitudinal axis. In usual practice, this roller is preferably cylindrically shaped and generally oriented perpendicular to the tank axis, its own axis being consequently horizontal in normal operation.
Some of these machines, in particular those that operate on a continuous basis, provide for an inversion of the roller rotation direction around the tank axis such that, when the waste causes a clogging and consequently blocks the forward motion of the roller, the latter will revert in the opposite direction and, after a complete revolution around the tank axis, will attack the clogging from the other side therof. Such inversion of the roller rotation direction is described in U.S. Pat. No. 5,579,688. It however turns out that this solution is not very fast since it suggets many back-and-forth motions of the roller around the tank axis before the destruction of this clogging has been achieved.
The object of the invention is to solve the problems which sometimes appear when using machines of this type, in particular when a machine is designed for continuous operation such that waste is thrown or otherwise introduced into the tank in variable and continuous quantities, while the compacting head is rotating. Since the waste supply into the tank is irregular, some local clogging phenomena may happen and impair proper compacting and/or shredding of the waste.
The object of the invention consequently is to provide a method that eliminates clogging in order to obtain a regular waste compacting, and a reduced volume inside a bag or other receptacle placed inside the tank
In a general manner, the method of the invention essentially includes the following steps:
a quantity indicative of the force exerted by said driving member is monitored, and
when said quantity exceeds a predetermined threshold, an unclogging operation is performed by
a) first raising said roller (16) up to a predetermined height, and
b) then releasing said roller (16) thus causing it to lower back onto the waste while being rotatively driven in the opposite direction.
Inasmuch as the compacting head continues rotating inside the tank while being raised, it can easily pass on top of a clogging point and simultaneously eliminate it. In such manner, the toothed roller first attacks and spreads the clogging zone, on one first side of this zone, while being raised. After having passed over the zone top if the returns onto the other side while rotating in the opposite direction around its own axis, so that the clogging normally is suppressed. Said unclogging operation is repeated if said effort or moment still exceeds said threshold after this motion in the opposite direction.
In this way, the compacting head directly attacks and destroys the clogging on the very zone it occupies, without requiring a complete revolution around the tank axis.
In a preferred case the roller that compacts the waste by pressing it under the compacting head weight, while this roller rotates around the tank axis, also performs a shredding of the waste material, which is particularly efficient since the roller is toothed and simultaneously rotating around its own axis. In this case, the invention may provide for an inversion of the roller rotation direction around its own axis, after the roller has been raised with the whole compacting head and the head rotation direction has been reversed. This improves the effect of the roller on the clogging, eases the shredding and consequently improves the compacting.
Advantageously, a single motor controls both rotation motions; in normal operation, the motor rotation direction is periodically reversed and the period of time between two successive normal inversions is longer than the unclogging operation duration. According to a particular embodiment of the invention which implements this feature, the unclogging operation will last 5 seconds at the most whereas the reversion period in a normal operation will, at least, last 20 seconds.
According to another aspect, the invention includes a machine for implementing preferably in an automatic manner the various steps of the method.
Such a machine advantageously includes means for detecting the force exerted by said driving member, means for stopping of said driving member as well as its operation in one rotation direction or its operation in the other rotation direction, and means for raising the compacting head, said detection means automatically acting upon said control means and said raising means.
This machine also advantageously includes means for detecting the height of the compacting head and providing a full-tank signal when said height exceeds a predetermined threshold: the full-tank signal triggers a delay time having a duration longer than the duration of said unclogging operation; and the machine is stopped if, and only if, the height of the compacting head continuously exceeds said full-tank threshold during said delay time. This avoids the risk of an unexpected machine standstill when the raising head height temporarily exceeds the full-tank level while the head is raised during an unclogging operation.
According to an advantageous feature of the invention, such raising means may include a pressure cylinder and the raising height is determined by the actuation duration of said cylinder.
According to another feature, favorably combined with the preceding one, the driving member may include a hydraulic motor, with said motor and said pressure cylinder being supplied through a same circuit from a motor-driven pump connected with a vessel for the hydraulic fluid.
The force detecting means preferably then includes a pressure detector, having a threshold, for measuring the supply pressure at the entrance of said motor.
The pressure cylinder can be arranged in a vertical housing arranged in the vicinity of said tank, with the compacting head bearing a shielding sheet that can be moved in front of said housing to prevent any waste penetration into said housing.
A shielding skirt can be attached to said compacting head so as to be tangentially movable with respect to the receptacle walls, to insure that any waste tending to escape from the tank during the shredding and compacting operations falls back into this tank. Such a skirt preferably is connected, or integral, with the compacting head: it as a result is completely disengaged from the tank when said compacting head is in its uppermost position so that the skirt does not impair the extraction of the receptacle, usually a flexible bag, out of the tank.
The machine may include detection means located at the same level as said compacting head and consisting of a cam integral with the compacting head and cooperating with a detector.
The machine of the present invention preferably is provided with several supply hoppers located around the cylindrical tank, which causes a uniform distribution of the waste after it has been introduced into the tank. Any clogging thus is of a lesser size and can be faster destroyed.